I. Technical Field
This invention relates to friction materials for improving wear resistance and reducing noise levels between high load bearing friction surfaces, and more particularly, for mechanical structures such as brakes, couplings, clutches and transmission systems, among others.
II. Discussion
Friction materials have been utilized for a number of years in industries such as the automotive component industry. Materials used in such friction coatings include, for example, graphite, ceramic powders, metal or metal oxide powders, heat hardenable phenolic resins, asbestos fibers, glass and carbon fibers, aramid fibers, steel wool, bentonite, mica and diatomaceous materials, among others. Typically, such friction materials are used to form molded friction bearing components.
By way of example U.S. Pat. No. 5,004,497 which issued Apr. 2, 1991 to Shibata et al. relates to a friction material containing 0.85 to 30% by weight of carbon fibers and 2 to 20% by weight of aramid fibers, wherein the aramid fibers preferably consist of para-aramid fibers and/or a combination of chopped aramid fibers and fibrillar aramid fibers
Another friction material is disclosed in U.S. Pat. No. 4,777,193 which issued Oct. 11, 1988 to Kani. The Kani patent discloses a molded resin composite of friction material for use in clutches of automobiles or similar parts, wherein the composition comprises inert fiber, a resin binder, an organic filler, and an inert filler wherein the inert filler contains zirconium silicate in an amount of from between about 0.1 to about 5.0% by volume based on 100% by volume of the total composition.
Still another friction material is disclosed in U.S. Pat. No. 4,654,381 which issued Mar. 31, 1987 to Kang et al. The compositions disclosed are characterized by the addition of any one of more than two cermet powders selected from the group consisting of (a) a powdered cermet comprising 75 to 50% by weight of a blended carbonaceous material and 25 to 50% by weight of the stainless steel alloyed iron; (b) a powdered cermet comprising 75 to 50% by weight of a blended carbonaceous material and 25 to 50% by weight of tungsten alloyed iron and/or molybdenum alloyed iron; and (c) a powdered cermet comprising 75 to 50% by weight of a blended carbonaceous material and 25 to 50% by weight of metallic iron; wherein the blended carbonaceous material is a mixture of 90 to 70% by weight of oil coats and 10 to 30% by weight of graphite with the cermet powder being added to the composition in an amount of 15 to 40% by weight based on the total weight of the composition.
None of the art known to the Applicant specifically relates to friction materials wherein metal sulfides are alloyed with iron powder with the resulting alloy being added to various metal based compounds commonly used for friction bearing components.
It is therefore an object of the present invention to provide an improved friction material which offers both friction stability and noise reducing capabilities.
It is another object of the present invention to provide a friction material which is durable in use.
It is still another object of the present invention to provide a friction material which provides wear resistance to both the friction bearing surface and the opposing contact surface.
According to the present invention, there is provided a friction material which includes the incorporation of metal sulfides alloyed with iron powders, wherein the resulting alloys are added to various metal based friction material compounds to provide a friction material with enhanced friction stability. This improved friction stability will generally be reflected in greater wear resistance along both the friction bearing surface and the opposing contact surface. Among the many metal sulfides which have proven useful, manganese sulfide has proven to be particularly useful.
According to a preferred embodiment of the present invention, a base friction material comprises between about 85% to about 99% by weight of a compound including varying amounts of pulp, steel fibers, iron powders, carbon, inert fillers and phenolic resins and about 1% to about 15% by weight of a metal sulfide--iron powder alloy. The metal sulfides which are alloyed with iron powder using known techniques generally include ZnS, FeS, MoS.sub.2, CuS.sub.2, TiS, CdS,Sb.sub.2 S.sub.3, MnS, CoS, Co.sub.3 S.sub.4, CaS, BaS, SrS, FeS.sub.2, ZrS.sub.2, Cu.sub.2 S, Ni.sub.3 S.sub.2, NiS, Ni.sub.3 S.sub.4, MnS.sub.2, CoS.sub.2, CoS.sub.2 S.sub.3, SnS.
The constituents of the base friction material are typically commercially available from a number of different sources. The metal sulfide-iron powder alloy can be introduced either as is or in the form of an admixture with other materials such as solid lubricants including antimony sulfide and aluminum phosphate, among others.
Further objects of the present invention reside in the method of utilizing the metal sulfide-iron powder alloy in the formation of friction bearing components.
The advantages of the present invention will become better understood by reference to the following detailed description.